1. Technical Field
The present invention relates generally to an apparatus and a method for the seawater pre-treatment for desalinating seawater into fresh water.
2. Description of the Related Art
In general, seawater desalination refers to obtaining fresh water by removing various impurities and salts from seawater, which contains salts. Generally, seawater desalination methods include an evaporation method, a reverse osmosis and a freezing method.
The evaporation method is a method for obtaining fresh water by a low-pressure evaporation system which performs evaporation by lowering pressure after supplying heat to seawater.
The reverse osmosis method is a method for extracting fresh water by filtering the ionic materials dissolved in seawater through a semipermeable membrane designed such that the ionic substances dissolved in water are substantially excluded from filtering and only pure water passes through. This reverse osmosis method has the advantage that consumption of energy is low and its operation is easy, as compared with the evaporation method, and so it has been widely used recently. In order to separate pure water and ionic materials from seawater, a pressure higher than that of the osmotic pressure is required. Reverse osmosis refers to this pressure. In the case of seawater desalination, it generally requires a high pressure of about 42 to 70 bar.
The seawater desalination facilities required by the reverse osmosis method may include a pre-treatment apparatus, a seawater desalination apparatus and an after-treatment apparatus in order to remove foreign materials and salts contained in seawater.
Among them, the pre-treatment device is intended to improve the desalination efficiency by removing in advance a foreign material contained in seawater before removing salt from seawater. In the case of not conducting the pre-treatment stage, there are problems in that a higher reverse osmosis pressure is required when removing salts from seawater by the reverse osmosis method and also foreign materials excessively adhere to the membrane, thus reducing the permeation of fresh water through the membrane.
In the conventional pre-treatment stage for desalination, seawater that is stored in a fixed volume in a storage tank is transferred to a sand filter or a multi-layer filter via a transfer pump to remove the primary impurities and, if necessary, organic impurities are removed by passing through the activated carbon filter.
The pre-treated water that has passed through the pre-treatment procedure is introduced into a reverse osmosis filtration device for desalination and separated into desalinated water and concentrated water. The concentrated water is discharged, and the desalinated water is mineralized and sterilized in the after-treatment stage and placed into a final storage tank.
Conventional pre-treatment facilities for seawater desalination have disadvantages in several aspects. For example, a high transfer pressure is required to remove foreign materials from seawater, the consumption of energy is high and several filtering steps need to be performed. Therefore, the devices are large in size and complicated.